This invention relates to unmanned air vehicles (UAVs) and more particularly to communications with air traffic control (ATC) stations involving UAVs.
There is an increasing usage of UAVs for a variety of applications, especially in airspace regulated by ATC. In the United States, the Federal Aviation Administration has standards for the safe operation of aircraft. Communications between ATC stations and aircraft plays a critical role in maintaining a safe environment for both aircraft and people aboard aircraft especially in regions where multiple aircraft are flying in proximity to one another. ATC systems normally rely on two-way analog radio frequency (RF) voice communications with aircraft operating in a region controlled by a particular ATC. In addition to voice communications, aircraft are normally required to have a transponder which transmits limited one-way communications identifying the aircraft to the ATC and certain other information.
During normal operation of a UAV, a remote human operator who may typically be based at an earth station is responsible for the operation and control of the UAV. Command and operational status information are transmitted between the remote human operator and the UAV by a two-way digital RF communication link, which may utilize other in-flight aircraft or satellites as communication repeaters between the UAV and an earth station where the human operator is located. In addition to supporting two-way digital communications, the UAV includes an RF transceiver which supports analog RF voice communications with ATC systems. The digital communication link between the UAV and human operator includes voice communication support so that a two-way voice communication path between an air traffic controller and the human operator is supported. Thus, the air traffic controller, from his point of view, is in normal voice communications with the “pilot” of the UAV just as in communicating with the pilot of a manned airplane. That is, the air traffic controller can give voice instructions to control the flight parameters, e.g. heading, altitude, speed, etc., of the UAV which will be heard by the remote human operator and acknowledged by a reply voice communication just like a pilot of a manned aircraft. Likewise, the human operator can initiate voice communications with the air traffic controller seeking permission for a change of the flight parameters of the UAV. Of course, such communications between the air traffic controller and the human operator requires the existence of the digital voice communication channel between the human operator and the UAV. Should the digital communication link (including command and control) between the human operator and the UAV fail, or just voice communication with the remote human operator fail, then two-way voice communications utilized by the air traffic controller for communications with the operator of the UAV will also fail. In the event of such a failure, the human operator may place a conventional landline telephone call from his earth station location to the subject air traffic controller in order to establish two-way communications via landline telephone with regard to the operation of the UAV. From an air traffic controller point of view, such a landline communication is substantially more difficult, includes at least an initial interval of time during which two-way voice communications are not available during the failure of the normal path, and, in general, is disruptive to the air traffic controller's attention required for the control of multiple aircraft under his supervision since landline usage is more burdensome.
It should be noted that the UAV normally stores in memory one or more default courses of action (alternate mission plans) that are automatically initiated upon the loss of digital communications with the human operator. For example, the UAV may be programmed to utilize stored data such as the location of its home base, landing field information and a series of actions to take in the event of loss of the digital communication link. Other information acquired directly by the UAV is of course available to the UAV such as its location based on GPS and operational flight parameters. This facilitates the capability of the UAV to autonomously fly itself back to its home base and land in the event of the loss of digital communications with the human operator. Alternatively, the UAV may follow any predetermined mission plan stored in memory. Should the digital communications link between human operator and the UAV become operative again, the human operator may issue a command to regain control of the UAV and abort the automated default actions.